feat(admin): implement initial admin dashboard and member management

This commit introduces the foundational structure for the admin dashboard, focusing on the member management feature.
Key additions include:

- A new page at `/admin/manage/members` to display and manage members.
- An `AddModal` component with a comprehensive form for creating new members, featuring validation with Zod and input
masking.
- A reusable `PhoneInput` component with country code selection, backed by a new `useCountries` composable and a full
country dataset.
- A custom, user-friendly global error page (`error.vue`) to handle application errors gracefully.
- Updated dashboard sidebar navigation to include the new member management section.
- Added recommended VS Code extensions and settings to improve developer experience.

app/composables/useDashboardSidebarLinks.ts

@@ -8,6 +8,19 @@ export const useDashboardSidebarLinks = () => {
         icon: "mdi:view-dashboard",
         to: "/admin/dashboard",
       },
+      {
+        label: "信息管理",
+        icon: "mdi:file-document-outline",
+        defaultOpen: true,
+        type: "trigger",
+        children: [
+          {
+            label: "会员籍管理",
+            icon: "mdi:account",
+            to: "/admin/manage/members",
+          },
+        ],
+      },
       {
         label: "内容管理",
         icon: "mdi:bookshelf",